In article , "AlexW"
says...
I need to compact several small areas of ground/chippings before laying
Indian stone slabs for light foot traffic. In the past I have rented a
plate compactor for this purpose.

For various reasons this is not going logistically easy or cost
effective this time though.

I was thinking of improvising a manual compactor with a big plug (say
30KG) of concrete with a 2x4 set in to it with through handles to lift
drop a few inches each time I pound.

ASCII diag:

||
==||== --- handles
||------ 2x4
||
##||##
#-||-# --- concrete plug, with screws/bolts to secure
######

Has anyone tried something similar? Did it work? Can anyone offer any
advice?

That sounds rather heavy to me - here's one you can buy

http://www.toolstation.com/?r=f&feature=77668

I saw one with a wooden handle in Wickes the other day but didn't
notice the price.